Nickel- and/or cobalt-based superalloys effective for use in high temperature environments are commonly used by the aerospace and power industries. While such alloys are inherently strong, they are generally not particularly resistant to corrosion by high temperature gases. Corrosion and oxidation-resistant coatings are therefore often applied to the superalloys to improve corrosion and/or oxidation resistance.
Internal coatings to protect those superalloy parts can be applied by several different methods. For example, chemical vapor deposition (CVD) methods using a reactor to generate a reactive Al-bearing species, or CVD methods that use above-the-pack technology, have been used. Both methods are generally effective, but require a sizable investment in equipment and the like. Moreover, in the case of above-the-pack processes, there is a significant amount of waste generated, including corrosive gases that require scrubbers to capture active species and/or convert them to innocuous products.